Posterior fixation system

ABSTRACT

A posterior fixation system includes a saddle member, an anchoring member, an occipital plate, an occipital rod, and a cross-link connector. The anchoring member anchors the saddle member to bone. The saddle member includes a pair of upright portions that define a channel. The channel is adapted to receive an orthopedic rod, and the saddle member can include a hole to receive the anchoring member. The saddle member and the anchoring member can be coupled so as to allow multi-axial movement of the members. The anchoring member in one embodiment is a screw coupled to the hole of the saddle, and in another embodiment, the anchoring member is a hook. The offset member may be coupled to the saddle member to allow for offset connection of rods. Connection of individual rods can be accomplished by connecting the rods with the cross-link connector. The cross-link connector has an integrally formed cylindrical member that couples a pair of coupling portions together. The cylindrical member can be bent along multiple axes. The occipital plate secures the rods to the occipital bone of the skull. The occipital plate has a cross-shaped plate with a plurality of apertures defined in the plate and at least one saddle member coupled to the plate. Alternatively, the occipital rod can be secured to the occipital bone.

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 09/663,638, filed Sep. 15, 2000, now U.S. Pat. No.6,485,491 all of which is incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention generally relates to orthopedic implants used forcorrection of spinal injuries or deformities, and more specifically, butnot exclusively, concerns apparatuses for fixing a portion of the spine,such as the cervical spine, to allow correction or healing thereof.

In the realm of orthopedic surgery, it is well known to use implants tofix the position of bones. In this way, the healing of a broken bone canbe promoted, and malformations or other injuries can be corrected. Forexample, in the field of spinal surgery, it is well known to place suchimplants into vertebrae for a number of reasons, including (a)correcting an abnormal curvature of the spine, including a scolioticcurvature, (b) to maintain appropriate spacing and provide support tobroken or otherwise injured vertebrae, and (c) perform other therapieson the spinal column.

Typical implant systems include several pieces, which commonly areuseful and may be associated with only specific other pieces. Bonescrews, hooks, and clamps are well know as fixation devices, which areconnected or adjoined to a particular bone as a connection between theremainder of the implant and the bone. Specially formed plates or rodsare commonly used as stabilization and support members. Thus, in acommon spinal implant system, a spinal plate is implanted along one ormore vertebrae by driving a bone screw through the plate and into eachof two vertebrae. The vertebrae are thus supported and kept in aparticular position by the plate, so as to promote healing. One exampleof such an instrumentation system is U.S. Pat. No. 5,735,853 to Olerud.

Alternatively, a rod can be used as the support and stabilizing member.In such an implant, a series of two or more screws are inserted into twoor more vertebrae to be instrumented. A rod is then placed within orcoupled to the heads of the screws, or is placed within a connectingdevice that links the rod and a screw head, and the connections aretightened. In this way, a rigid supporting structure is fixed to thevertebrae, with the rod providing the support that promotes correctionof the vertebral malformation or injury.

Many varieties of bone fixation devices (e.g. screws and hooks) aremonoaxial in construction. That is, such devices are connected to therod or plate such that a longitudinal axis through the rod or plate anda longitudinal axis through the fixation device are capable of only asingle position with respect to each other. While useful in certaincircumstances, in many therapeutic situations the degree of precisionrequired to use such an inflexible device is impractical, or can lead toa longer duration of surgery, potentially awkward angles for the surgeonand for the patient, with the potential for attendant complications suchas pain and/or extended rehabilitation.

More recently, bone fixation devices having multi-axial capability havebeen introduced. Examples of such constructs are shown in U.S. Pat. Nos.5,797,911, 5,954,725, and 5,810,818. These devices help to reduce therequired precision of placement of the fixation device, since a headportion of the fixation device is multi-axially positionable around thebone-threaded or hook portion. The head can thus be positioned so as toeasily receive the rod, limiting or removing much of the positioningdifficulty inherent in prior devices.

Most such devices are designed for spinal fixation at the thoracic andlumbar levels. Accordingly, there is a need in the art for acomprehensive multi-axial spinal implant system, and particularly onethat is useful in the cervical region of the spine.

SUMMARY OF THE INVENTION

One form of the present invention is a unique multi-axial boneattachment assembly. Other forms concern a unique spinal implant system,a unique orthopedic fixation plate, a unique cross-link connector, andanother unique multi-axial bone attachment assembly.

A further form of the present invention is directed to a uniquemulti-axial bone attachment assembly that includes a saddle member, abone anchoring member, and a washer (crown member). The saddle memberhas a plurality of upright portions that define a channel through thesaddle member. The saddle member further has a hole therethrough boundedby an inner wall, and the hole forms a lower opening in the saddlemember. The bone-anchoring member extends through the opening. Thebone-anchoring member includes a head portion and an anchoring portion.The washer has a recessed portion for accommodating an orthopedic rodand may include a radially extending projection. The washer is fittedwithin the hole of the saddle member and atop the bone-anchoring member.

Yet another form concerns a unique spinal implant system. A saddlemember has a plurality of upright portions that define a channel throughthe saddle member. The saddle member further has a transverse holedefined through the upright portions that is transverse with respect tothe channel. A bone-anchoring member is coupled to the saddle member foranchoring the saddle member to bone. An offset member is adapted tocouple to an orthopedic rod, and the offset member has a coupling memberand a body adapted to couple to the rod. The coupling member extendsfrom the body and through the transverse hole of the upright members.

Another form is directed to a unique cross-shaped orthopedic plate. Theplate includes a cross-shaped member. The cross-shaped member has alongitudinal axis connecting first and second longitudinal ends and atransverse axis connecting first and second transverse ends. Thecross-shaped member has a plurality of apertures therethrough. At leastone saddle member is attached to the cross-shaped member, and the saddlemember has a plurality of upright portions that define a channel throughthe saddle member.

A further form concerns a unique cross-link connector. The connectorincludes a plurality of coupling ends each adapted to couple to anorthopedic rod. A cylindrical member is integrally connected to thecoupling ends. The cylindrical member has a cylindrical shape forpermitting multi-axial bending of the cylindrical member.

Still yet another form is directed to a unique multi-axial boneattachment assembly. A saddle member has a plurality of upright portionsthat define a channel through the saddle member. The saddle memberfurther has a hole therethrough bounded by an inner wall, and the holeforms a lower opening in the saddle member. A bone-anchoring memberextends through the opening. The bone-anchoring member includes acoupling portion provided in the hole for permitting multi-axialmovement of the anchoring member and an anchoring portion. An expansionmember is coupled to the anchoring member for expanding the couplingportion in order to lock the anchoring member into position.

The present invention provides a modular fixation system that allows asurgeon multiple treatment options for patients, allowing the surgeon toadapt the treatment to specific patient anatomy. The conceptssurrounding the present invention are specifically designed for cervicalvertebral fixation, but could be extended to include thoracic, lumbarand sacral fixation. Other advantages and objects of the presentinvention will be evident in view of the following specification anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial cross-sectional view of a bone anchor assemblyaccording to one embodiment of the present invention.

FIG. 2 shows a side view of a saddle member according to the embodimentshown in FIG. 1.

FIG. 3 shows a cross-sectional view of the saddle member taken alongline III-III in FIG. 2.

FIG. 4 shows a top view of the saddle member of FIG. 2.

FIG. 5 shows an enlarged cross-sectional view of the saddle member takenalong line V-V in FIG. 3.

FIG. 6 shows a side view of an anchor member according to oneembodiment.

FIG. 6 a shows a side view of an anchor member according to anotherembodiment.

FIG. 7 shows an enlarged cross-sectional view of threads of theembodiment of the anchor member shown in FIG. 6.

FIG. 8 shows a top view of the anchor member of FIG. 6.

FIG. 9 shows a perspective view of a washer according to one embodimentof the present invention.

FIG. 10 shows a top view of the washer of FIG. 9.

FIG. 11 shows a cross-sectional view of the washer of FIG. 9

FIG. 12 shows a top view of another embodiment of a washer according tothe present invention.

FIG. 13 shows a side view of a set screw according to one embodiment ofthe present invention.

FIG. 14 shows a top view of the set screw of FIG. 13.

FIG. 15 shows a side view of a set screw according to another embodimentof the present invention.

FIG. 16 shows a top view of the set screw of FIG. 15.

FIG. 17 shows a perspective view of a snap ring for use in the presentinvention.

FIG. 17 a shows a side view of an alternative embodiment of a snap ringfor use in the present invention.

FIG. 18 shows a top view of the snap ring of FIG. 17.

FIG. 19 shows a top view of an orthopedic plate according to oneembodiment.

FIG. 20 shows a side view of the orthopedic plate of FIG. 19.

FIG. 21 shows a cross-sectional view of the orthopedic plate taken alongline XXI-XXI in FIG. 19.

FIG. 22 shows a cross-sectional view of a portion of the orthopedicplate taken along line XXII-XXII in FIG. 19.

FIG. 23 shows a cross-sectional view of a portion of the orthopedicplate taken along line XXIII-XXIII in FIG. 20.

FIG. 24 shows a perspective view of a bone anchor assembly according toanother embodiment of the present invention.

FIG. 25 shows a perspective view of an embodiment of a hook member ofthe assembly of FIG. 24.

FIG. 26 shows a front view of the hook member of FIG. 25.

FIG. 27 shows a perspective view of the bone anchor assembly of FIG. 24prior to assembly.

FIG. 28 shows a partial cross-sectional view of an offset memberaccording to another embodiment of the present invention.

FIG. 28 a shows a partial cross-sectional view of an offset memberaccording to a further embodiment of the present invention.

FIG. 29 shows a side view of the offset member of FIG. 28.

FIG. 30 shows a top view of the offset member of FIG. 28.

FIG. 31 shows an end view of the offset member of FIG. 28.

FIG. 32 shows a cross-sectional view of the offset member of FIG. 28.

FIG. 33 shows a side view of an offset member and a set screw accordingto a further embodiment of the present invention.

FIG. 34 shows a cross-sectional view of the offset member of FIG. 33.

FIG. 35 shows a top view of the offset member of FIG. 33.

FIG. 36 shows an end view of the offset member of FIG. 33.

FIG. 37 shows an end view of the set screw of FIG. 33.

FIG. 38 shows a cross-sectional view of the set screw taken along lineXXXVIII-XXXVIII in FIG. 37.

FIG. 39 shows a cross-sectional view of the set screw of FIG. 37.

FIG. 40 shows a side view of a cross-link connector according to anotherembodiment of the present invention.

FIG. 41 shows a top view of the cross-link connector of FIG. 40.

FIG. 42 shows an enlarged view of a portion of the cross-link connectorof FIG. 40.

FIG. 43 shows a cross-link connector with an arched cylindrical member.

FIG. 44 shows an end view of a set screw according to another embodimentof the present invention.

FIG. 45 shows a cross-sectional view of the set screw taken along lineXLV-XLV in FIG. 44.

FIG. 46 shows a perspective view of a bone anchor assembly according toa further embodiment of the present invention.

FIG. 47 shows an exploded view of the bone anchor assembly of FIG. 46.

FIG. 48 shows a cross-sectional view of a hook member.

FIG. 49 shows a top view of an occipital-cervical rod.

FIG. 50 shows a side view of an occipital-cervical rod.

FIG. 51 shows a cross-sectional view of the occipital-cervical rod takenalong line LI-LI in FIG. 49.

FIG. 52 shows a cross-sectional view of the occipital-cervical rod takenalong line LII-LII in FIG. 49.

FIG. 53 shows a partial cross-sectional view of a bone anchor assemblyaccording to another embodiment of the present invention.

FIG. 54 shows a cross-sectional view of an embodiment of a saddle membershown in FIG. 53.

FIG. 55 shows a top view of the saddle member of FIG. 54.

FIG. 56 shows a cross-sectional view of a washer shown in FIG. 53.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purpose of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the illustrated device, and such further applicationsof the principles of the invention as illustrated therein, beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

In FIG. 1, there is shown an embodiment of a multi-axial bone anchorassembly 20 according to the present invention. Bone anchor assembly 20includes a saddle member 22, a bone anchoring member 24, and a washer(crown member) 26. In some embodiments, assembly 20 will further includea C-shaped snap ring 28 and a set screw 30, which are fitted with saddlemember 22 as will be described hereafter.

As shown in FIGS. 1-4, saddle member 22 generally has a U-shape, withtwo upright portions 32 defining a channel 34 extending through saddlemember 22. Channel 34 is then configured to accommodate an elongatedmember 36, such as a spinal rod. For posterior cervical fixation, rod 36may have one of a number of desired lengths. As seen in FIG. 1, thewidth of channel 34 is slightly larger than the diameter of rod 36,which allows easier insertion of rod 36 into channel 34, also allows forcompensation for contouring of the rod, and allows use of a range of rodsizes with the same saddle member 22. Saddle member 22 further includesa hole 38 therethrough, hole 38 being in one particular embodimentsubstantially perpendicular to channel 34 and substantially parallel toupright portions 32.

In a particular embodiment of saddle member 22, illustrated in FIGS.2-5, upright portions 32 each have an outer surface 40 and an innersurface 42. Inner surfaces 42 are parallel to hole 38, along alongitudinal axis of saddle member 22. Outer surfaces 40 are angled withrespect to inner surfaces 42 and the longitudinal axis of saddle member22. In one specific embodiment, outer surfaces 40 have an inward taper43, which taper allows for easier handling of the saddle member 22 andreduced bulk of saddle member 22. Near the bottom of saddle member 22,hole 38 is narrowed by a wall portion 44. Below wall portion 44, hole 38opens outward by virtue of a conical wall portion 46. Conical wallportion 46 allows bone anchor member 24 to be positioned in any of aninfinite number of angular positions relative to saddle member 22 byreducing interference of the lower portion of saddle member 22 with ashank portion of bone anchor member 24.

The illustrated embodiment of saddle member 22 further includes an innergroove 48 that extends around hole 38. Groove 48 is configured toaccommodate snap ring 28 in a compressed condition, i.e., the outerdiameter of groove 48 is at least slightly smaller than the normaluncompressed outer diameter of snap ring 28. The illustrated embodimentof saddle assembly 22 further includes a trough 50 extendinglongitudinally within each of upright portions 32. Trough 50accommodates placement of washer 26, as further described below, and mayhave a rounded (e.g. cylindrical), squared, or other appropriate shapeto accommodate washer 26. Upright portions 32 further include aninternally threaded portion 52, as shown in FIGS. 1 and 3. Internallythreaded portions 52 are configured to be threadedly coupled with setscrew 30, as described hereafter.

As shown in FIGS. 6-8, one embodiment of the bone anchor member 24 ofthe present invention has a threaded portion 56 and a head portion 58.In a specific embodiment, threaded portion 56 includes a thread 60having a forward or leading flank 62 and a rearward or load flank 64 anda root surface 66, in which load flank 64 and root surface 66 form anacute angle. Such an acute angle between load flank 64 and root surface66 may be termed a “reverse angle” thread.

Head portion 58 of bone anchor member 24 includes a lower head portion68 and an upper head portion 70. Lower head portion 68 is generallyconvex, and in one embodiment forms part of a sphere. In the illustratedembodiment, the lower head portion 68 extends from a shank portion 72 ina direction away from threaded portion 56, and stops at/or before atangent to lower head portion 68 would be parallel to a longitudinalaxis L of bone anchor member 24. Upper head portion 70 is also generallyconvex, and forms a part of a sphere in the illustrated embodiment.Upper head portion 70 is diametrally smaller than lower head portion 68and head portions 68 and 70 are connected by a lip 74. A tool-engagingrecess 76 is formed in upper head portion 70, and may extend into lowerhead portion 68. In another embodiment shown in FIG. 53, head portion 58a of bone anchor member 24 a does not have a lip 74.

Referring now to FIGS. 9-11, there is shown an embodiment of washer 26of the present invention. Washer 26 includes an upper portion 80, alower portion 82, and a hole 84 therethrough. Upper portion 80 and lowerportion 82 may be constructed integrally or may be separatelyconstructed and attached together in any known manner. An upper surface86 of upper portion 80 includes recessed portions 88 in the illustratedembodiment, which recessed portions 88 form a part of a cylinder sizedand configured to accommodate placement of an elongated member (such asrod 36 of FIG. 1) therein. Lower portion 82 further includes an uppersurface 83 that faces snap ring 28.

Referring now to FIG. 11, washer 26 has a hole 84 provided through bothupper portion 80 and lower portion 82. Hole 84 includes a lower concavesurface 96 and a cylindrical surface 98. Concave surface 96 in onespecific embodiment has a spherical shape so as to substantiallycoincide with a portion of upper head portion 70 of anchoring member 24.Lower portion 82 is generally in the shape of a circular disc, andincludes two projections 90 extending radially therefrom. Projections 20in conjunction with troughs 50 align recessed portions 88 of washer 26with channel 34 and prevent rotation of washer 26 so as to minimizemisalignment between rod 36 and recessed portions 88.

In one embodiment, shown in FIGS. 9-10, projections 90 each include twosubstantially planar side surfaces 92, and an end surface 94 that isrounded and may form a portion of a cylinder. Projections 90 are sizedand shaped so as to fit and slide easily within the troughs 50 uprightportions 32 of saddle member 22. In another embodiment illustrated inFIG. 12, projections 90 a each include a rounded end surface 100.

Multi-axial bone anchor assembly 20 can further include a set screw 30.As illustrated in FIGS. 13-16, set screw 30 is generally cylindrical andhas external threads 102. External threads 102, in one embodiment, arebuttress threads. In another embodiment, threads 102 could be reverseangle threads so as to minimize splaying between the two upright members32. An example of such reverse angle threading is disclosed in U.S.patent application Ser. No. 09/188,825, which is hereby incorporated byreference.

Set screw 30, in the embodiment illustrated in FIGS. 13-14, has at oneend a tool-engaging portion 104. Tool-engaging portion 104 has a roundedend surface 106 and substantially planar tool-engaging surfaces 108.Since end surface 106 is rounded, internal trauma to a patient can bereduced. Tool-engaging surfaces 108, in one embodiment, are oriented ina hexagonal configuration. Once set screw 30 is secured to saddle member22, tool engaging portion 104 can be sheared off or otherwise removed soas to further reduce the profile of assembly 20. As illustrated in FIGS.15-16, another embodiment of set screw 30 a includes a substantiallyflat end surface 110 in order to minimize the profile of assembly 20.Set screw 30 a further includes a tool-engaging bore 112. Tool-engagingbore 112 is used in conjunction with a tool for introducing set screw 30a into saddle member 22.

In certain embodiments, multi-axial bone anchor assembly 20 includessnap ring 28 in order to secure washer 26 against anchoring member 24.One embodiment of such a snap ring 28 is shown in FIGS. 17-18. Snap ring28 has a central opening 114 and a compression slot 116 defined therein.Snap ring 28 further has a first surface 118, an opposite second surface120, an inner lateral surface 122 defining opening 114, and an outerlateral surface 124. Compression slot 116 allows snap ring 28 tocompress and fit into inner groove 48 of saddle member 22. The diameterof the entrance of groove 48 is at least slightly smaller than the outerdiameter 126 of an uncompressed snap ring 28. Opening 114 of snap ring28 has an inner diameter, which allows snap ring 28 to fit around upperportion 80 of washer 26. One of the surfaces 118 and 120 engage theupper surface 83 of lower portion 82 in order to secure washer 26. Snapring 28 can have a square cross-section, as shown in FIG. 1, or acircular or other appropriate shape cross-section, and in one particularembodiment is made of a shape memory alloy such as nitinol.

Another embodiment of snap ring 28′ is illustrated in FIG. 17 a. Snapring 28′ is non-planar, and in one embodiment has a series ofundulations forming relative crests 129 a and relative troughs 129 btherein. Alternatively, non-planar snap ring 28′ could have other curvedconfigurations, or could have extending finger-spring elements along it.When assembly 20 (or assembly 262 described below) is assembled,non-planar snap ring 28′ allows less play between saddle member 22,anchoring member 24 and washer 26 (or similar parts of assembly 262,described below) because non-planar snap-ring 28′ fills a greaterportion of groove 48 of saddle member 22.

An embodiment of an orthopedic fixation plate 130 according to thepresent invention is illustrated in FIGS. 19-23. In one form, orthopedicplate 130 is secured to the occipital bone of a skull. However, itshould be appreciated that plate 130 can be secured to other bones.Orthopedic plate 130 includes a cross-shaped member 132 having a firstlongitudinal arm (end) 134 to a second longitudinal arm (end) 136 alonga longitudinal axis. Cross-shaped member 132 further has a firsttransverse arm (end) 138 and a second transverse arm (end) 140 connectedtogether along an axis transverse with respect to the longitudinal axis.Orthopedic plate 130 further includes a pair of saddle members 22 aintegrally formed on or joined to longitudinal arms 134 and 136. Itshould be appreciated that saddle members 22 can also be pivotallycoupled to cross-shaped member 132 so as to provide greater positioningfreedom. As illustrated in FIG. 22, saddle members 22 a each include apair of upright members 32 a and a channel 34 a defined between uprightmembers 32 a. Upright members 32 a include threaded portions 52 aconfigured to be threadedly coupled to a set screw 30 in a manner asdescribed above.

Orthopedic plate 130, in one embodiment, includes a set of apertures142. Bone anchors 24 b (FIG. 6 a) are secured in apertures 142 in orderto secure plate 130 to the occipital bone of the skull. As shown in FIG.6 a, anchor 24 b includes a head portion 58 b having a convex underside59 a, which may be spherical, and a beveled top 59 b around atool-engaging recess 59 c. Apertures 142 shown in FIGS. 19-23 for theparticular embodiment are provided on both the longitudinal arms 134,136 and the transverse arms 138, 140 in a cross configuration in orderto provide greater stability. As shown in FIG. 23, aperture 142 includesa lower conical portion 144 and an upper conical portion 146. Lowerconical portion 144 widens towards a lower surface 148 of orthopedicplate 130, and upper conical portion 146 widens towards an upper surface150 of orthopedic plate 130. Upper and lower conical portions 144, 146allow a bone screw to be easily positioned at varying angular positionsrelative to orthopedic plate 130. In one embodiment, opposing walls oflower conical portion 146 are oriented at about sixty degrees (60°) withrespect to one another, and opposing walls of upper conical portion 146are oriented at about forty-five degrees (45°) with respect to oneanother. Cross member 130 further includes a beveled outer peripheralsurface 152 between lower surface 148 and upper surface 150.

In one particular embodiment, cross member 132 is curved along thelongitudinal axis between longitudinal arms 134 and 136, and is alsoslightly curved along the transverse axis. This curvature of crossmember 132 allows orthopedic plate 130 to better match the contour ofthe occipital bone of the skull. It should be understood that crossmember 132 can also be curved along only one of the axes orsubstantially flat along both axes or can be otherwise contoured priorto or during surgery in order to match specific patient anatomy.

In FIG. 24, there is shown another embodiment of a multi-axial boneanchor assembly 160 according to the present invention. Anchor assemblyincludes a saddle member 162 and an offset connector 164 coupled tosaddle member 162. As shown in FIGS. 25-26, saddle member 162essentially includes the same features as described above in referenceto saddle member 22. Saddle member 162 includes two upright portions 32b defining channel 34 b. Channel 34 b is configured to accommodate anelongated member 36 b. Upright portions 32 b each has outer surface 40 bthat is angled with respect to inner surface 42 b. Upright portions 32 bfurther include an internally threaded portion 52 b. Internally threadedportions 52 b are configured to be threadedly coupled with set screw 30.

Additionally, saddle member 162 includes a transverse hole 166 definedin both upright portions 32 b. Transverse hole 166 is orientedtransverse with respect to channel 34 b, and transverse hole 166 isadapted to receive a rod (such as rod 36 in FIG. 1) or offset connector164. This configuration between channel 34 b and transverse hole 166provides a physician with greater flexibility during surgery, sinceoffset connector 164 can be oriented at different angles with respect tosaddle member 162. Offset connector 164 further can be laterallypositioned at any of an infinite number of distances from saddle member162, because transverse hole 166 passes through both upright portions32. Further, saddle member 162 is dually useful, because a rod (such asrod 36 in FIG. 1) or offset connector 164 can be coupled to eitherchannel 34 b or transverse hole 166.

Saddle member 162, in one embodiment, further includes a hook member 168for engaging bones in a generally known manner. Hook member 168 has acurved portion 170 extending from upright portions 32 and asubstantially straight portion 172 extending from curved portion 170.Straight portion 174 has a beveled bottom surface 174, which reducestrauma when hook member 168 is attached. It should be appreciated thathook member 168 could be replaced with another anchoring member, such asanchoring members 24 or 24 a (FIGS. 6, 53) in order to attach saddlemember 162 to a bone.

Referring now generally to FIGS. 27-32, offset connector 164 includes acoupling member 176 integrally formed or otherwise joined to a body 178.In one form, coupling member 176 is a cylindrical rod. Body 178 has arod receiving bore 180 that is adapted to receive rod 36 and a threadedbore 182 that intersects rod receiving bore 180. A set screw 30 isscrewed into threaded bore 182 in order to secure rod 36 to offsetconnector 164. Body 178 further can include a beveled outer edge 184(FIG. 27) in order to minimize trauma to a patient. In anotherembodiment shown in FIGS. 28-32, rod receiving bore 180 has a slot 186defined therein. Edges 187 are formed between slot 186 and rod receivingbore 180. Edges 187 along with set screw 30 provide three lines ofcontact with a rod 36 coupled to offset connector 164 so as tostrengthen the connection. In still yet another embodiment shown in FIG.28 a, offset connector 164 a has a pair of upright portions 32 cdefining a channel 34 c adapted to receive a rod. Upright portions 32 chave internally threaded portions 52 c for engaging a set screw 30.

Referring now to FIG. 27, offset connector 164 is coupled to saddlemember 162 by inserting coupling member 176 in direction A intotransverse hole 166. Set screw 30 is used to secure coupling member 176to saddle 160. Offset connector 164 can be laterally positioned withrespect to saddle member 162 by moving coupling member 176 withintransverse hole 166.

An offset connector 188 along with a set screw 189 according to stillyet another embodiment of the present invention are shown in FIGS.33-39. As shown in FIGS. 33-36, offset connector 188 includes a couplingmember 176, and a pair of laterally oriented body members 190 and 192. Achannel 194 is defined between body members 190 and 192, and channel 194is adapted to receive rod 36. One of the body members 192 is slightlylonger than the other and has a threaded bore 196 defined therein. Setscrew 189 is threaded into bore 196 so as to secure rod R to offsetconnector 188. As illustrated in FIGS. 37-39, set screw 189 is generallycylindrical and has threads 198. Set screw 189 further has a toolengaging bore defined in one end and a pointed tip 202 at the other end.Pointed tip 202 engages rod 36 when rod 36 is coupled to offsetconnector 188.

A cross-link connector 204 according to one embodiment, which isillustrated in FIGS. 40-42, is adapted to be bent about multiple axes.Cross-link connector 204 has a pair of coupling ends 206 integrallyconnected together with a cylindrical member 208. The cylindrical shapeof cylindrical member 208 allows cross-link connector 204 to be bent inany of an infinite number of directions. In one particular embodimentshown in FIG. 43, cylindrical member 208 a is pre-formed with an arch soas to avoid any obstructions between the two ends 206. Each coupling end206 includes a threaded bore 210 with an opening 211 in which a setscrew 30 is threaded and a curved member 212 that defines a cavity 214adapted to receive rod R. Opening 215 of cavity 214 is defined in a sideof cross-link connector 204 opposite opening 211 of threaded bore 210.This configuration allows cross-link connector 204 to be secured toadjacent rods after the adjacent rods are situated within the patient.In one embodiment, threaded bore 210 is positioned at about fifty-fivedegrees (55°) relative to a longitudinal axis that extends between theends 206. Cross-link connectors are used to link adjacent rods within apatient. An obstruction (such as another rod or bone) may prevent atypical cross-link connector from linking adjacent rods together. Thecross-link connector 204 of the present invention solves this problem bybeing adapted to bend along multiple axes.

One embodiment of a set screw 216 that is adapted to be threaded intothreaded bore 210 is illustrated in FIGS. 44-45. Set screw 216 has oneend with a tool engaging bore 218, a rod engaging end 222 and a threadedportion 220 provided between both ends. Rod engaging end 222 has afrusto-conical portion 224 adjacent threaded portion 220 and a flatportion 226, which frusto-conical portion 224 contacts rod 36. In oneform, frusto-conical portion 224 has an angle 228 of about forty degrees(40°).

In FIG. 46, there is shown a multi-axial bone anchor assembly 230according to another embodiment of the present invention. Assembly 230has a generally U-shaped saddle member 22, which was described abovewith reference to FIGS. 2-5, coupled to a hook anchor member 168 a. Inthis embodiment, saddle member 22 may be formed without groove 48. Aspreviously discussed, saddle member 22 has a pair of upright portions 32that define channel 34. Set screw 30 is threadedly secured to threadedportion 52 of saddle member 22 in order to secure rod 36 to saddlemember 22. As shown in FIGS. 47-48, hook member 168 a has a curvedportion 170 a and a substantially straight portion 172 a. In thisembodiment, hook member 168 a further includes a coupling (head) portion232 that is coupled to saddle member 22. Coupling portion 232 includescoupling members 234 and a threaded hole 236 adapted to receiveexpansion member 238. In one form, coupling portion 232 includes fourmembers 234 having a part-spherical outer surface and expansion member238 is a set screw. In one form, expansion member 238 at one end has atool engaging portion 240 and a threaded portion 242 at the other endfor securing expansion member 238 into hole 236. Expansion member 238further includes an expansion portion 244 located between tool engagingportion 240 and threaded portion 242. Expansion portion 244 contacts andexpands semispherical members 234 to anchor saddle member 22 to hookmember 168 and prevents further rotation. In one form, expansion portion244 has a conical shape.

In use, coupling portion 232 is inserted into hole 38 through the bottomof saddle member 22. When saddle member 22 is coupled to hook member 168a, the spherical shape formed between semispherical members 234 allowssaddle member 22 to rotate about multiple axes. Expansion member 238,once secured in hole 236 causes coupling members 234 to splay intocontact with saddle member 22, thereby fixing the relative positionbetween saddle member 22 and hook member 168.

An embodiment of an occipital-cervical rod 246, which can be attached tothe above-described assemblies, is illustrated in FIGS. 49-52.Occipital-cervical rod 246 includes a plate portion 246 a, through whicha plurality of apertures 248 are formed, and a rod portion 246 b.Apertures 248 may be oblong in shape. Defined along plate portion 246 aare an upper surface 250, a curved lower surface 252, and a pair ofbeveled side surfaces 254 between upper surface 250 and lower surface252. Each aperture 248 includes an upper portion 256 that widens towardsupper surface 250 and a lower portion 258 that widens towards lowersurface 252. Grooves 260 are defined around plate portion 246 a ofoccipital-cervical rod 246 and between adjacent apertures 248. Bonescrews 24 b (FIG. 6 a) are inserted into apertures 248 in order tosecure plate portion 246 a to the occipital bone of a patient. Rodportion 246 b extends along the spinal column and can be attached to thespinal column using the above-described or other connectors.Alternatively, plate portion 246 a can be attached to one or morevertebrae using bone screws 24 b (FIG. 6 a), and rod portion 246 b canextend upward and be attached to the occipital bone using screws, hooks,cable, or other attachment members.

In FIG. 53, there is shown another embodiment of a multi-axial boneanchor assembly 262 according to the present invention. Bone anchorassembly 262 includes a saddle member 22 d, a bone anchoring member 24a, and a washer 26 d. Bone anchoring member 24 a does not have a lip 74.In some embodiments, assembly 262 will further include a C-shaped snapring 28 and a set screw 30, which are fitted with saddle member 22 d ina manner described below.

As shown in FIGS. 54-55, saddle member 22 d generally has a U-shape,with two upright portions 32 d defining a channel 34 d extending throughsaddle member 22 d. Channel 34 d is then configured to accommodate anelongated member 36 (as described above). Saddle member 22 d furtherincludes a hole 38 d therethrough, hole 38 d being in one particularembodiment substantially perpendicular to channel 34 d and substantiallyparallel to upright portions 32 d. Upright portions 32 d are angled in amanner similar to the one as described above with reference to FIGS.2-3. Near the bottom of saddle member 22 d, hole 38 d is narrowed by awall portion 44 d. Below wall portion 44 d, hole 38 d opens outward byvirtue of a wall portion 46 d. Wall portion 46 d allows bone anchormember 24 a to be positioned in any of an infinite number of angularpositions relative to saddle member 22 d by reducing interference of thelower portion of saddle member 22 d with a shank portion of bone anchormember 24 a.

The particular illustrated embodiment of saddle member 22 d furtherincludes an inner groove 48 d. As illustrated, groove 48 d extendsaround hole 38 d, and in this particular embodiment, groove 48 d isuniform between a top portion of groove 48 d and the bottom portionthereof. Groove 48 d is configured to accommodate snap ring 28 in acompressed condition. Groove 48 d has a thickness 264 that is, in oneform, thicker than snap ring 28. Further, the illustrated embodiment ofsaddle assembly 22 d in FIGS. 54-55 does not include a trough 50 thatextends longitudinally within each of upright portions 32 d. Uprightportions 32 d further include internally threaded portions 52 d, whichare configured to be threadedly coupled with set screw 30.

Referring now to FIG. 56, there is shown another embodiment of washer 26d according to the present invention. Washer 26 d includes an upperportion 80 d, a lower portion 82 d, a snap ring recess 266, and a hole84 d therethrough. Upper portion 80 d, lower portion 82 d, and snap ringrecess 266 may be constructed integrally or may be separatelyconstructed and attached together in any known manner. Snap ring 28 fitswithin recess 266 in order to secure washer 26 d within saddle member 22d. In one embodiment, assembly 262 is assembled by inserting anchoringmember 24 a through hole 38 d in saddle member 22 d. Washer 26 d, withsnap ring 28 in at least a portion of recess 266, is then inserted intohole 38 d. Snap ring 28 contracts into recess 266 as washer 26 d goesthrough saddle member 22 d, and expands into groove 48 d to hold washer26 d within saddle member 22 d. An elongated member is then inserted inchannel 34 d, and a set screw (such as those described above) isthreaded into internally threaded portions 52 d, saddle member 22 d tolock the elongated member, washer 26 d and anchoring member 24 atogether.

Washer 26 d has a hole 84 d provided through both upper portion 80 d andlower portion 82 d. Hole 84 d includes a lower concave surface 96 d anda cylindrical surface 98 d. Lower concave surface 96 d is adapted toaccommodate head portion 58 a of anchor member 24 a. In the particularembodiment illustrated in FIG. 56, lower portion 82 d is generally inthe shape of a circular disc. In this particular embodiment, lowerportion 82 d does not have projections 90.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character. It should be understoodthat only the preferred embodiments have been shown and described andthat all changes and modifications that come within the spirit of theinvention are desired to be protected.

1. A cross-link connector, comprising a single-piece connector bodyincluding: a plurality of coupling ends each configured to fixedlyengage a portion of an orthopedic rod; and a cylindrical memberintegrally spanning between said coupling ends to define saidsingle-piece connector body, said coupling ends including a curvedmember that defines a cavity adapted to receive said rod, saidcylindrical member having a cylindrical shape for permitting multi-axialbending of said cylindrical member in an infinite number of directions;and wherein said cylindrical member is arched between said couplingends, and wherein said coupling ends have respective upper surfaces thatare substantially planar with each other and said cylindrical member hasan upper surface above said plane of said coupling end upper surfaces.2. The cross-link connector of claim 1, wherein each of said couplingends includes a threaded bore and a set screw received in said bore forsecuring said rod.
 3. The cross-link connector of claim 1, furthercomprising a first elongated element contacting a first coupling end,and a second elongated element contacting a second coupling end.
 4. Thecross-link connector of claim 1, wherein said coupling ends have alongitudinal axis, and are open in a direction of lateral of said axis.5. The cross-link connector of claim 1, wherein said coupling ends eachinclude a curved portion having a concave surface for contactingrespective rods, and said curved portion is integral with saidcylindrical member.
 6. A cross-link connector, comprising: asingle-piece connector body including: a pair of coupling ends eachhaving a substantially smooth opening for accommodating a spinal rod anda threaded aperture communicating with said opening for accommodating aset screw; a bridging member integral with and extending between saidcoupling ends to define said single-piece connector body, said bridgingmember having a substantially cylindrical central portion permittingmulti-axial bending of said member in an infinite number of directions,a first tapered portion integrally linking said central portion to afirst of said coupling ends, and a second tapered portion integrallylinking said central portion to a second of said coupling ends; and apair of set screws, each adapted to thread into said threaded apertureof at least one of said coupling ends and press a rod against a portionof said coupling end; and wherein said bridging member is arched, andwherein said coupling ends have respective upper surfaces that aresubstantially planar with each other and said cylindrical centralportion has an upper surface above said plane of said coupling end uppersurfaces.
 7. The cross-link connector of claim 6, wherein said bridgingmember is arched sufficiently to provide a space between said bridgingmember and the spinal cord canal when said cross link connector isimplanted.
 8. The cross-link connector of claim 6, wherein said bridgingmember is arched sufficiently so that at least a portion of saidbridging member is above or even with the surface of the bone.
 9. Thecross-link connector of claim 8, wherein said portion of said bridgingmember is above or even with the body of a cervical vertebra.
 10. Thecross-link connector of claim 6, wherein said connector is adapted to besecured to adjacent rods after the adjacent rods are situated within apatient.
 11. The cross-link connector of claim 6, wherein said couplingends have a longitudinal axis, and are open in a direction of lateral ofsaid axis.
 12. The cross-link connector of claim 6, wherein said centralportion of said bridging member has a longitudinal axis, and whereinsaid threaded apertures have respective longitudinal axes that aresubstantially planar with said longitudinal axis of said central portionof said bridging member.
 13. The cross-link connector of claim 6,wherein said central portion of said bridging member is substantiallyplanar; and wherein said threaded apertures have respective longitudinalaxes that are substantially planar with said central portion of saidbridging member.
 14. The cross-link connector of claim 6, wherein saidcoupling ends each include a curved portion having a concave surface forcontacting respective rods, and said curved portion is integral withsaid bridging member.
 15. A cross-link connector, comprising asingle-piece connector body including: a plurality of coupling ends eachconfigured to fixedly engage a portion of an orthopedic rod; and acylindrical member integrally spanning between said coupling ends todefine said single-piece connector body, said coupling ends including acurved member that defines a cavity adapted to receive said rod, saidcylindrical member having a cylindrical shape for permitting multi-axialbending of said cylindrical member in an infinite number of directions;and wherein said cylindrical member is arched between said couplingends, and wherein said coupling ends have respective upper surfaces thatare substantially planar with each other and said cylindrical member hasan upper surface above said plane of said coupling end upper surfaces;and wherein each of said coupling ends includes a threaded bore and aset screw received in said bore for securing said rod; and wherein eachsaid bore communicates with the cavity of its respective coupling endand is between the cavity of its respective coupling end and saidcylindrical member.
 16. A cross-link connector, comprising: asingle-piece connector body including: a pair of coupling ends eachhaving a substantially smooth opening for accommodating a spinal rod anda threaded aperture communicating with said opening for accommodating aset screw; a bridging member integral with and extending between saidcoupling ends to define said single-piece connector body, said bridgingmember having a substantially cylindrical central portion permittingmulti-axial bending of said member in an infinite number of directions,a first tapered portion integrally linking said central portion to afirst of said coupling ends, and a second tapered portion integrallylinking said central portion to a second of said coupling ends; and apair of set screws, each adapted to thread into said threaded apertureof at least one of said coupling ends and press a rod against a portionof said coupling end; and wherein said bridging member is arched, andwherein said coupling ends have respective upper surfaces that aresubstantially planar with each other and said cylindrical centralportion has an upper surface above said plane of said coupling end uppersurfaces; and wherein each said threaded aperture is between saidopening of its respective coupling end and said central portion of saidbridging member.